Origin and Habitat: Arrojadoa dinae ssp. eriocaulis is endemic to Brazil, where it is found in the eastern drainage of Serra do Espinhaço in northern Minas Gerais up to the border area of Bahia (The extent of occurrence is quite large, approximately 4,700 km2, but the area of occupancy is estimated to be below 500 km2). It occurs in two disjunct areas, at elevations of 700 to 1,100 m asl: the northern subpopulation grows in the mountains east of the towns of Monte Azul and Mato Verde, while the southern subpopulation is found in Grao Mogol. The subpopulations are small and fragmented. Each subpopulation has less than 500 individuals, and there are no more than 5,000 mature individuals in total.Habitat and Ecology:A species of the campo rupestre element, it is found in sandy cerrado. The generation length is around 10 years. The population is declining in the northern part due to fires, deforestation, and sand quarrying. Arrojadoa eriocaulis is also threatened by illegal collection. The entire plant as well as its seeds are collected for ornamental use.

Description:Arrojadoa dinae is a low succulent shrub with slender stems, basally branching with subterranean tubers. The ssp. eriocaulis (firstly described as Arrojadoa eriocaulis by Buining & Bredero in 1973) is distinctive in having a covering of white wool, typically with only 8-9 ribs, yellowish brown spines, and light violet-pink flowers. Arrojadoa dinae and A. eriocaulis are often understood as different species. In fact in some places like the area northeast of Mato Verde, A. eriocaulis and A. dinae grow together without hybridizing, this would confirm the thesis of two distinct, indipendent species. Stems: Slender, cylindrical, very fine, up to about 30 cm tall,Ribs: 8-9. Areoles: Round, closely set, at first very woolly, later almost bare. Flowering areoles different from non flowering, tufted with bristles and hairs.Spines: Yellowish brown.Cephalia: With cm long.Flowers. The tubular flowers appear near the apex, among thick white wool and brownish bristles, that form a pseudocephalium, creating a kind of ring around the stem, through which the cactus continue its growth. The flower-tube is often, brownish red to violet-pink, to 30 mm long and 9 mm in diameter, the pericarpel and tube naked, the limb very short pale violet-pink or white, stamen and style not projecting. This species start blooming when about 20 cm tall.

Subspecies, varieties, forms and cultivars of plants belonging to the Arrojadoa dinae group

Arrojadoa dinae, Arrojadoa multiflora, Arrojadoa eriocaulis and Arrojadoa beateae are a group of distinct but related species in Minas Gerais and Bahia. They are readily distinguished by their subterranean tubers, stems, wood anatomy, bi-colored flowers, and fruits. Most authors regard them as conspecific under the oldest name Arrojadoa dinae. However some studies in the field, show that it should be better to maintain these taxa as separate species. In some cases they even grow together (A. dinae, A. eriocaulis) without hybridization.

Cultivation and Propagation: Arrojadoa dinae subs. eriocaulis is not particularly difficult on own roots providing it is given a little extra heat during the winter, but this and all its relatives do best when grafted. Arrojadoas bloom on the forest floor all year-round and are accustomed to receiving lots of summer rain and winter dew, so they never dry out for long in the wild. They most definitely are not desert plants and don't survive if treated as such. In arid climates they fare best in containers, where the roots remain moist longer. Growth rate: It is a relatively rapidly growing and easily flowering species that will make clumps given the best conditions. Soils: It likes very porous standard cactus mix soil and can also be grown in orchid bark, or on cork sheets or a tree branch like for epiphytes.Repotting: Use pot with good drainage.Watering: It should be watered generously during the growing season, keep drier in winter. Water them less than average if in bigger pots.Fertilization: Feed with a high potassium fertilizer in summer. Hardiness: Reputedly sensitive to frost (in his biotope the temperature never drops below 15 ° C), but less so if kept on the dry side prior to, and during, cold weather. However warmth throughout the year will increase the grower's success (not less than 8-12°C during rest season). Exposition: Outside bright, hot conditions or afternoon shade, inside it needs bright light, and some direct sun. Strong light encourages flowering and heavy wool and spine production. Uses: It is an excellent plant for container growing. It always looks good and stays small. Pests & diseases: It may be attractive to a variety of insects, but plants in good condition should be nearly pest-free, particularly if they are grown in a mineral potting-mix, with good exposure and ventilation. Nonetheless, there are several pests to watch for: - Red spiders: Red spiders may be effectively rubbed up by watering the plants from above.- Mealy bugs: Mealy bugs occasionally develop aerial into the new growth among the wool with disfiguring results, but the worst types develop underground on the roots and are invisible except by their effects. - Scales: Scales are rarely a problem.- Rot: Rot is only a minor problem with cacti if the plants are watered and “aired” correctly. If they are not, fungicides won't help all that much.Propagation: The Arrojadoas are quite easy to grow from cuttings, seed or (often) graft. Seeds germinate in 7-14 days at 21-27° C in spring, remove the glass cover gradually as the plants develops and keep ventilated, no full sun for young plants! To make a cutting twist off a branch and permit it to dry out a couple of weeks, lay it on the soil and insert the stem end partially into the soil. Try to keep the cutting upright so that the roots are able to grow downward.